OK, I've been meaning to write this for a long time. Especially after going to some fantasy/anime conventions and seeing steampunk guys in full gear. I knew some of them from before and being a bit of a gun crank (the old term for gun nut, only less derogatory), and one of the things that I commented on were their obviously fake guns that they had. One guy had a steampunk rocket launcher that he described as 'throwing out a rocket and igniting the fuel with a pilot light'. I went on to describe the various issues such a device would have, most notably the backblast that would go directly back into the launcher and shooter. This is the reason why bazookas were designed as they were and the training to make sure that neither the shooter nor the loader are anywhere near the backblast area where they would be incinerated instantly. I also found another guy with a nerf gun designed as an oversized pistol and I practically explained how such a thing would 'work' if it was a real gun. I probably taught him a thing or two about firearms.
That being said, it did make me think about the general idea of firearms in a dieselpunk setting. In the actual time frame, the guns that someone from the 1920s to 50s would have would vary dramatically. In the early part, the 1920s and 30s, most guns would be of pre-WW1 era design. I mean think of the major pistols we think of as the sidearm of adventurers, gangsters, and military heroes. Colt 1911, Mauser C96, Colt 1903 pocket hammerless (or FN M1910 if they're European, it was as big there as the pocket hammerless was in the US), Luger and others... all designed pre-WW1. Even after WW2, there were so many surplus WW2 era guns that your typical post-WW2 era dieselpunk adventurer/detective/whatever could still be using most of the same stuff. Except for the submachine guns and (post WW2) early assault rifles, which saw a huge amount of advancements during WW2.
This made me think... what exactly would constitute a 'dieselpunk' gun? I mean games like Wolfenstein Old Blood had a lot of 'what ifs' of real or fake WW2 era German guns. Like the assault rifle in the is clearly based on the StG 44. They have an auto-shotgun in the game called a Schockhammer, and while it is pretty cool, the thing I got from its appearance is it seemed too big to be effective. This is the biggest issue I have when visualizing machinery and guns. I mean when imagining giant airships, a lot of handwaving is needed because the science behind stuff like that can get weird when designing flying aircraft carriers with internal hangars and stuff... but I find it hard to do the same with guns. Maybe it's because I'm too familiar with guns in RL, or maybe it's because unlike airships, robots, or weird vehicles, guns can successfully designed in weird ways and still function, but if I see something on a gun that just would impede it's use in RL, it's hard for me not to ask 'who designed this and why?'. Oversized, unergonomical, and over/underpowered weapons in a nominally semi-realistic setting just don't seem to make internal sense even within the worlds they exist in.
In real life, look at the STEN and the AUSTEN. The STEN is already fairly diesel, but the AUSTEN looks like a STEN taken to dieselpunk levels. The reverse also exists... kinda. The current British service rifle is the SA80 which entered service in 1985 but after WW2 the British took the lessons they learned from the war and figured they needed their next generation service weapon to be an assault rifle. They designed the EM-2 rifle using an intermediate 7mm round.
Just look at the two and compare them... they look almost exactly the same.
So here I'm posing the question. How would you define a dieselpunk firearm? What is or is not dieselpunk in a gun? Would having firearms with features developed primarily during and after WW2 work in a setting supposedly happening in the interwar era? What say you.
I actually wrestle with this a bit, as well. It's actually fairly easy to build an impractical steampunk gun, as much of steampunk is by its nature, impractical. But dieselpunk tends to be more streamlined, more functional. I have made a shotgun out of copper tubing and fittings that was an attempt at diesel weaponry, but wasn't 100% satisfied with it. Others were impressed, but all I saw was plumbing parts. I've been working on a design for a pistol for a while, but I have given up on it a few times. I want something that looks functional, something slightly over-stylized, but that looks like it could already exist in this world. I recently acquired some pieces to use a handle scales for a pistol that is going to help bring it into focus, I'm hoping.